Air filter



FIG. 1 is a bottom, front, right side perspective view of an air filter showing our new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a left side elevation view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The dash-dot broken lines adjacent to the shaded areas represent boundaries of the claimed design and form no part thereof. All other broken lines represent unclaimed portions of the air filter and form no part of the claimed design. 

CLAIM The ornamental design for an air filter, as shown and described. 